Hydraulic sheet-stretching machines

ABSTRACT

A hydraulic sheet-stretching machine with a stretching grip and a stationary counter-grip, with means for the axial adjustment and arresting of these grips, and a stretching cylinder with a cylinder crossbeam and a stretching piston, the machine being erected in a foundation pit having side walls which form a powertransmitting connection between the cylinder crossbeam and the counter-grip, the cylinder crossbeam and the counter-grip being provided with means supporting them against axial thrust, the said supporting means bearing against the side walls of the foundation pit.

United States Patent Priebe [451 Aug. 22, 1972 1 1 HYDRAULIC SHEET-STRETCHING 3,038,520 6/1962 Elger ..72/302 MACHINES FOREIGN PATENTS OR APPLICATIONS [72] Inventor: Fritz Priebe, Duisburg, Germany 27,345 1/ 1909 Great Britain ..72/302 Asslgneer schloemann Aktiensesellschafl, 1118- 801,888 9/1958 Great Britain ..72/311 Seldoff, Germany 739,291 10/1955 Great Britain ..72/293 22 u d: No 25 1969 838,632 6/1960 Great Britain ..72/302 [211 App! No 879 822 243,516 12/1925 Great Britain ..72/311 Primary Examiner-Charles W. Lanham Assistant Examiner-Michael J. Keenan [30] N lf l ggg 2 Priority l I 225 9 Attorney-Holman, Glascock, Downing & Secbold 0v. ermany ABSTRACT 12?} li'fi'if'jijiiij:5:3:jJJJJJi::JJJJJJJI::JiJiJJiJYf/fiilifii AhydraulicSheermtchingmashinewithStretching [58] Field of Search ..72/293, 296, 302, 316, 378, P samnary 72/3 297 axial ad ustment and arresting of these grips, and a stretching cylinder with a cylinder crossbeam and a stretching piston, the machine being erected in a foun- [56] References Cited dation pit having side walls which form a power-trans- UNXTED STATES PATENTS mittititriig connection betiweenrtle cylindgr crossgealni an e counter-grip, t e cy 111 er cross cam an t e 2,218,503 10/1940 Brooks etal ..72/302 countebgrip being provided with means supporting 2,476,556 7/1949 Maize ..72/296 them against axial thrust, the id supporting means 53?]; gi bearing against the side walls of the foundation pit.

once a 2,352,442 6/ 1944 Loewy et al. ..72/302 5 Claims, 2 Drawing Figures -Ipulp,ll% A 32 21, c8

HYDRAULIC SHEET-STRETCHING MACHINES This invention relates to a hydraulic machine for stretching metal sheets or plates, with a stretching grip and a counter-grip with members for the axial adjusting and arresting thereof, and with a stretching cylinder with its cylinder crosshead, and a stretching piston, the machine being erected in a foundation pit.

It is know to erect sheet-stretching machines of massive construction in foundation pits, so as to have better supervision of the stretching operation and of the machine itself, and also in order to improve manipulation when introducing a fresh sheet. All disturbing pipes are in this way arranged in the pit. On grounds of safety, also, this arrangement is advantageous in the event of a rupture of the sheet occuring during the stretching, when the surroundings might be endangered.

A known massive sheet-stretching machine (DAS No. 1,255,074) is constructed in such a way that the stretching force exerted by drives consisting of cylinders and pistons is transmitted by a closed rectangular aggregate, the two transverse sides of which are formed by the two gripper heads and the two long sides of which are formed by the two drives, each consisting of a cylinder and a piston, and by longitudinally extending pressure members in alignment therewith, the axes of the cylinder-and-piston drives and the axes of the longitudinally extending pressure members lying in a common plane, which also contains the longitudinal axis of the workpiece to be stretched. This arrangement prevents any bending moments that may otherwise be operative in the pressure members during the stretching operation, besides the thrust to be taken up. With very great stretching forces the pressure members would however have to be very rigidly constructed, in order to obviate possible buckling.

In the case of another stretching machine, disclosed in German Patent No. 1,084,676, round rods are employed as thrust or pressure members. The pistons and cylinders of the stretching machine again lie in one plane with these round rods and with the axis of the material that is being stretched, and are arranged in the middle of the round rods, in order to shorten the buckling length.

All these thrust members, on account of the very high stretching forces, are of very massive and heavy constructions, and thereby considerably increase the expense of producing the stretching machine erected in a foundation pit. Moreover the adjusting of the clamping heads or grips to the actual length of a sheet has hitherto required a stepwise displacement and arresting of the counter-grip in the thrust members. The accurate adjusting to the particular length of sheet is however effected by the stretching grip, so that here the stroke of the stretching cylinder must comprise, besides the actual racking stroke, an additional stroke to compensate for the differences in length arising from the stepwise adjusting of the counter-grip to the length of the sheet.

The object of the present invention is to provide a massive sheet-stretching machine which will be capable of stretching large metal plates with an appropriate expenditure of force, without excessive expense being involved on account of the thrust members, which for these heavy machines are of considerable importance,

and wherein the adjusting of the grips to the appropriate length of sheet is effected in a simple manner.

According to the invention this aim is attained by the fact that the lateral walls of the foundation pit form the power-transmitting connection between the cylinder cross-beam and the countergrip. By this means the result is advantageously obtained that the usual thrust members of steel, and/or the frame, can be entirely omitted, since the lateral walls of the foundation pit, which in any case are as a rule made of reinforced concrete, take up the thrusts from the stretching operatron.

In a further development of the invention, the countergrip is of stationary construction, and is supported in an axial direction in the lateral foundation-pit walls. ln the same manner the cylinder cross-beam of the stretching cylinder is supported in an axial direction in the lateral foundation-pit walls. The counter-grip therefore needs no power drive for its axial movement. Locking means provided in the usual manner at definite distances apart in the thrust members for the adjustment to particular lengths of the sheet are omitted.

in order to enable this adjusting to the particular length of sheet to be effected, the stretching grip, in a further development of the invention, is directly adjustable steplessly, independently of the stretching piston, the direct stepless adjusting of the stretching grip being effected by means of a screw-threaded spindle journalled in the stretching piston, which is made hollow.

In this manner it is possible to limit the actual stretching stroke of the stretching piston to the effective extension stroke or stretching stroke for the sheet. With the conventional machines, besides the actual stretching stroke, it has always also been necessary to take into consideration additionally the removal also, which, notwithstanding the stepwise adjustment of the counter-grip to the particular length of sheet, yielded an additional difference in length between the two grips. Owing to the provision of a screw-threaded spindle between the stretching piston and the stretching grip, it is possible, with a stationary counter-grip. to effect a stepless adjustment of the stretching grip to the particular sheet length without the stroke of the stretching piston having to be longer than is necessary for the actual stretching operation of the longest sheet with the greatest possible racking. Furthermore, owing to the arrangement of the spindle in the stretching piston, the stretching grip is pulled directly. The construction otherwise usual, in single-cylinder machines with stretching crossbar and tension columns between cross-bar and stretching grip, is here also omitted.

As a further development of the invention, the stretching grip is pivotally connected with the threaded spindle, and pairs of lateral supporting rollers arranged symmetrically in relation to the stretching axis are allocated to this stretching grip, to support it against the walls of the foundation pit. By these rollers the stretching grip is guided on the side walls of the foundation pit, and is also supported thereon when an eccentric force occurs owing to a flaw in a sheet. Any obliquity of the stretching grip is thereby obviated. This pivotal connection does not give rise to a bending stress on the threaded spindle.

In an advantageous further development of the invention the stretching grip and the counter-grip are made of forged steel. Owing to the higher stresses that are admissible with this material, as compared with the conventional cast steel or the welded constructions in the form of sheet-metal laminations, the grips may be made comparatively small.

On the basis of the arrangement of these massive sheet-stretching machines according to the invention, but particularly on account of the absence of special thrust members, the weight of this sheet-stretching machine according to the invention is considerably reduced as compared with that of know thrust-member constructions.

One embodiment of the invention will now be further described by way of example, as illustrated in the accompanying drawings, in which:

FIG. 1 is a side view of the machine, partly in longitudinal section; and

F IG. 2 is a plan view, wherein the stretching cylinder and the stretching piston are represented in longitudinal section.

ln a foundation pit 1, there is on the left-hand side of the drawing a stretching cylinder 2, which is axially supported with its cylinder crossbeam 3 upon carrier supports 6, arranged in recesses in the side walls 4 of the foundation. On the right-hand side is stationarily arranged a counter-grip 7, which is axially supported with lateral corbels 8 upon carrier supports 9, located in recesses 5 in the lateral foundation walls 4. Facing the carrier support 6 of the cylinder crossbeam 3 and the carrier supports 9 of the corbels 8 of the counter-grip 7, damping elements 10 are provided, which may consist of bonded rubber or similar cushioning material, and are effective with possible sheet ruptures.

In order to minimize bending moments acting on the cylinder crossbeam 3, in the left-hand region of the foundation pit, the side walls 4 in the present example are drawn in somewhat closer to the axis of the machine than in the central region.

In the stretching cylinder 2, which is open at both ends, a hollow stretching piston 11 of stepped construction, supplied with pressure fluid at one end, is longitudinally displaceable. It is energized by way of an inlet 12 in the stretching cylinder 2. In the end of this cylinder facing the counter-grip 7 a spindle nut 13 is rotatably arranged, and is secured against axial displacement by a holding ring 14. A toothed wheel 15 secured upon the outer end of the spindle nut 13 meshes, either by way of an intermediate toothed wheel 18 or directly, with a pinion 16 of a spindle-driving motor 17.

The driven spindle nut 13 guides and drives a screw threaded spindle 19, which is secured by holders 4] against rotating and which is pivotally connected with the stretching grip 20. By means of the driven spindle nut 13, the stretching grip 20 is axially and steplessly displaceable by way of the threaded spindle 19.

Upon the right-hand end of the threaded spindle 19 is secured by means of screw threads a jointed piece 21, which carries bolt heads 22 arranged diametrally in a vertical plane. The end of the stretching grip 20 pointing towards the threaded spindle 19 is provided with a corbel or projection 23, which is flattened above and below. In it is secured in a vertical plane a joint bolt 24.

Two joint plates or lugs 25 connect the threaded spindle l9 pivotally with the stretching grip 20 by way of the joint bolt 24 and the bolt heads 22.

The stretching grip 20 is axially displaceable upon running wheels 26, which are guided upon rails 27. Pairs of supporting rollers 28 arranged laterally on the stretching grip 20 and symmetrically about the stretching axis run upon carrier support 29 secured to the side walls 4 of the foundation pit, and there support the stretching gn'p 20, if a bending moment is exerted thereon in consequence of a sheet tearing.

The stretching piston 11 carries at its end facing the stretching grip 20, a flange-like retracting ring-piece 30 Between this retracting ring-piece 30 and a collar 3] on the outside wall surface of the stretching cylinder 2 are supported hydraulically actuated retracting cylinders 32 and pistons 33.

These retracting cylinders 32 also act as brake cylinders in the event of the fracture of a sheet, for the masses accelerated by the energy liberated by the stretching head 20, the threaded spindle l9 and the stretch piston 11.

The foundation pit comprises at the left-hand end a slot like aperture 34, located in the stretch-cylinder axis, into which the threaded spindle 19 can enter to a greater or less extend according to the length of the sheet to be stretched.

In the stretching grip 20 and in the counter grip 7 are provided a number of wedge-shaped clamping jaw holders 35, which are connected, by way of rod-and-lever mechanism 36 including double-armed levers 37, with hydraulically actuated clamping jaw cylinders 38. In the clamping jaw holders 35 are inserted in a known manner clamping jaws 39, which reliably clamp the sheet 40 to be stretched. By means of the levers 37 the transmission ratio for the clamping force provided by the clamping jaw cylinder 38 can be varied. Alternatively however, a direct drive may be provided, with the lever 37.

lclaim:

l. A hydraulic sheet stretching machine installation comprising a movable gripperhead, a relatively fixed gripperhead, a stretching piston interconnected with said movable gripperhead, a stretching cylinder wherein said stretching piston is slidable, a transverse stretching cylinder crossbeam, said crossbeam defining means for extending into a first pair of opposed recesses in the side walls of a foundation pit in which the machine is installed, the relatively fixed gripperhead including lateral projections defining means for extending into a second pair of opposed recesses in the side walls of the foundation pit, the engagement of the stretching cylinder crossbeam and the relatively fixed gripperhead with the side wall recesses enabling reactive compression forces to be absorbed by the side walls of the foundation pit during sheet stretching.

2. A hydraulic sheet-stretching machine as claimed in claim I, further comprising means for axially adjusting the stretching grip steplessly and directly, independently of the stretching piston.

3. A hydraulic sheet-stretching machine as claimed in claim 2, the stretching piston being hollow and the means for steplessly and directly adjusting the stretching grip consisting of a screw-threaded spindle joumalled in the hollow stretching piston.

6 4. A hydraulic sheet-stretching machine as claimed pit. in claim 3, the stretching grip being pivotally connected 5. A hydraulic sheet-stretching machine as claimed with the screw-threaded spindle, and th hi in claim 1, the stretching grip and the counter-grip further comprising pairs of lateral supporting rollers being made Offorged Swelsupporting it against the side walls of the foundation 5 

1. A hydraulic sheet stretching machine installation comprising a movable gripperhead, a relatively fixed gripperhead, a stretching piston interconnected with said movable gripperhead, a stretching cylinder wherein said stretching piston is slidable, a transverse stretching cylinder crossbeam, said crossbeam defining means for extending into a first pair of opposed recesses in the side walls of a foundation pit in which the machine is installed, the relatively fixed gripperhead including lateral projections defining means for extending into a second pair of opposed recesses in the side walls of the foundation pit, the engagement of the stretching cylinder crossbeam and the relatively fixed gripperhead with the side wall recesses enabling reactive compression forces to be absorbed by the side walls of the foundation pit during sheet stretching.
 2. A hydraulic sheet-stretching machine as claimed in claim 1, further comprising means for axially adjusting the stretching grip steplessly and directly, independently of the stretching piston.
 3. A hydraulic sheet-stretching machine as claimed in claim 2, the stretching piston being hollow and the means for steplessly and directly adjusting the stretching grip consisting of a screw-threaded spindle journalled in the hollow stretching piston.
 4. A hydraulic sheet-stretching machine as claimed in claim 3, the stretching grip being pivotally connected with the screw-threaded spindle, and the machine further comprising pairs of lateral supporting rollers supporting it against the side walls of the foundation pit.
 5. A hydraulic sheet-stretching machine as claimed in claim 1, the stretching grip and the counter-grip being made of forged steel. 